Tong Chuan, Wang Liyuan, Wang Kun, Fu Jianxin
School of Civil Engineering, University of Science and Technology Beijing, Beijing 100083, China.
Shandong Gold Group (Laizhou) Co., Ltd., Jiaojia Gold Mine, Yantai 261441, China.
Materials (Basel). 2025 Jul 10;18(14):3253. doi: 10.3390/ma18143253.
This study systematically investigates the effects of shell ash (SA) content (0-10%) on early moisture evolution, pore structure, and hydration kinetics in cement paste using LF-NMR and NG-I-D hydration kinetic models. Key findings include the following: (1) Increased SA content significantly alters moisture phase distribution. Low contents (≤8%) consume free water through rapid CaO hydration, promoting C-S-H gel densification. However, 10% SA causes reduced moisture in 0.16-0.4 μm gel micropores (due to hindered ion diffusion) and abrupt increases in 0.63-2.5 μm pores. (2) Porosity first decreases then increases with SA content, reaching minimum values at 3-5% and 8%, respectively. The 10% content induces abnormal porosity growth from localized over-densification following polynomial fitting (R = 0.966). (3) Krstulovic-Dabic model analysis reveals three consecutive hydration stages: nucleation-growth (NG), phase boundary reaction (I), and diffusion control (D). The NG stage shows the most intense reactions, while the D stage dominates (>60% contribution), with high model fitting accuracy (R > 0.9). (4) SA delays nucleation/crystal growth, inducing needle-like crystals at 3% content. Mechanical properties exhibit quadratic relationships with SA content, achieving peak compressive strength (18.6% increase vs. control) at 5% SA. This research elucidates SA content thresholds governing hydration kinetics and microstructure evolution, providing theoretical support for low-carbon cementitious material design.
本研究使用低频核磁共振（LF-NMR）和NG-I-D水化动力学模型，系统地研究了壳灰（SA）含量（0-10%）对水泥浆体早期水分演化、孔隙结构和水化动力学的影响。主要研究结果如下：（1）SA含量增加显著改变了水分相分布。低含量（≤8%）通过快速的CaO水化消耗自由水，促进C-S-H凝胶致密化。然而，10%的SA导致0.16-0.4μm凝胶微孔中的水分减少（由于离子扩散受阻），而0.63-2.5μm孔隙中的水分突然增加。（2）孔隙率随SA含量先降低后增加，分别在3-5%和8%时达到最小值。10%的含量在多项式拟合后（R = 0.966），由于局部过度致密化导致孔隙率异常增长。（3）Krstulovic-Dabic模型分析揭示了三个连续的水化阶段：成核-生长（NG）、相边界反应（I）和扩散控制（D）。NG阶段反应最强烈，而D阶段占主导地位（贡献>60%），模型拟合精度高（R > 0.9）。（4）SA延迟成核/晶体生长，3%含量时诱导针状晶体形成。力学性能与SA含量呈二次关系，5% SA时达到峰值抗压强度（比对照组提高18.6%）。本研究阐明了控制水化动力学和微观结构演化的SA含量阈值，为低碳胶凝材料设计提供了理论支持。
